1988 Fiscal Year Final Research Report Summary
Mechanism of the Earthquakes with M Equal to or Greater than 7 that Occurred in Volcanoes (Including Calderas) and Their Relation to Volcanic Activity
| Project/Area Number |
62540291
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
固体地球物理学
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| Research Institution | Kyoto University |
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Principal Investigator |
KUBOTERA Akira Faculty of Science, Kyoto University, Professor, 理学部, 教授 (70025229)
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| Co-Investigator(Kenkyū-buntansha) |
KOBAYASHI Yoshimasa Faculty of Science, Kyoto University, Associate Professor, 理学部, 助教授 (80027284)
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| Project Period (FY) |
1987 – 1988
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| Keywords | Earthquakes occurred in the volcano / Very-low-frequency earthquake / Swarm earthquake / Shimabara earthquake / 伊豆大島地震(1986) |
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| Research Abstract |
In the present project we concentrated mainly on the Sakurajima earthquake 1914 and the Shimabara earthquake 1922 and tried to elucidate their relation to the respective volcanic activity and subsurface structure of volcanic body.
In 1987, we collected and analysed as many seismograms as possible at JMA stations and universities for both earthquakes. No satisfactory quantitative result was obtained because of insufficient quality of seismographs in those days and lacking information on the instrument. Macroseismic data such as time sequence, intensity distribution, or damage distribution and a comparison with recent results of micro-earthquakes observation and gravity anomaly show both earthquakes to be VL type due to slow faulting characteristic in volcanic areas.
In 1988, we investigated a M 6.0 earthquake of 1986.11.22. accompanying the Izu-Oshima eruptions to supplement the results in the preceding year. Some seismograms exhibited remarkably long-period vibrations (10-60 sec) suggesting the earthquake to be L or VL type. We computed spectra of about 30 seismograms of the JMA-59 type seismometers at JMA stations. the spectra revealed a lower corner frequency than that of a standard M 6.0 earthquake, and the long-period vibrations are explained by Rayleigh and Love waves generated from the same origin as the body waves.
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